1. Field of the Invention
The present invention relates to an apparatus for converting the energy available from water motion to electrical energy. More specifically, the energy available from the rise and fall in water level whether caused by waves or waves and tidal changes is converted to and stored as hydraulic energy. The controlled release of this hydraulic energy is transformed via a turbine-electric generator combination to a continuous source of electrical energy.
2. Prior Art
An apparatus for producing power from water waves is described in U.S. Pat. No. 2,848,189 issued to Caloia Aug. 19, 1958. That apparatus described a series of shore mounted levers to drive a series of piston pumps. That portion of the lever arms which extended seaward were of varying lengths so that while one arm might be in the trough of the wave another arm might be at the crest of the wave. The motion of the waves produces the up and down motion of the levers which drives the piston pump, the output of which drives a fluid motor, the spent fluid from which is stored in a reservoir to be recycled back to the piston pumps.
This invention has several limitations upon which the present invention improves. As the seaward lever arm gets longer and longer, and the float gets farther and farther from the lever fulcrum post, unless the piston pump is moved a similar distance away from the fulcrum point, the pumping action is progressively decreased for a given size wave. Therefore, to produce any degree of efficient pumping this apparatus is limited to use near seawalls, cliffs, etc. Again because of the inefficiency of the lever action substantial waves would be required to produce effective pumping action. This conclusion is contrary to the teaching of the inventor at lines 40-42 of the patent.
The present invention overcomes this limitation by using short lever arms which are all the same length. Therefore, the pumping efficiency as measured by the ratio of the distance the piston moves in and out to the distance the float moves up and down is the same for each arm. Further, the use of a water motion magnifier to raise the level of the wave and tidal action above its natural level ensures that the present invention will operate with small waves and tidal changes.
A second limitation of the Caloia invention concerns the connection of the lever to the piston rod. In addition to the frictional wear and tear at the connection point, the length of the rectangular slot controls the maximum amplitude the lever arm to which the float is attached can move up and down. The rectangular slot must be long enough to accomodate both mild and stormy seas. The longer the slot, the weaker the connection.
The present invention cures this problem by employing long horizontally mounted piston pumps. By employing a series of pivot points the up and down wave motion is translated essentially friction free to the in and out piston motion with negligible potentially damaging side to side forces. The use of long in length piston pumps means that the piston action can take place in different sections of the cylinder depending on the level of the water.
A third limitation of the Caloia invention is that while the apparatus incorporates an accumulator to smooth the distribution of energy when the pumping action is insufficient to maintain the desired output, no provision is made to release energy when the pumping action is too vigorous. The present invention incorporates with the accumulator and reservoir a dump valve-check valve system which permits excess pressure in the accumulator to be released to the reservoir which is vented to the atmosphere. The Caloia invention uses one accumulator per piston pump. In the present invention, the number of accumulators is independent of the number of piston pumps and depends only on the desired safety period. This is the time period the stored energy must be able to drive the turbine while the piston pump is either inoperable or operating at diminished capacity.
A U.S. Pat. No. 4,281,257 issued to Testa et al on July 28, 1981 describes a wave power generator. In this device, the up and down wave action is converted through levers and pivot points to a horizontal in and out motion by which air is compressed into a tank. The compressed air is then used to drive an air turbine or air grinder.
In a Japanese patent, issued in September 1981, Nakamura describes a compressed air storage device. The compressed air is produced by piston pump driven by the up and down motion of waves. Klein in German Patent Document dated October 1981, describes a reservoir-accumulator hydraulic system which is pressurized by the action of waves impinging on the walls of a cell.
Kammerer in U.S. Pat. No. 3,5125,889 issued on June 2, 1970 describes a power generation apparatus for use with offshore oil rigs which converts wave action into electrical energy. The energy conversion means utilized hydraulic pumps, hydraulic motors and an electrical accumulator such as batteries.